Polish riot police used tear gas and water cannon at migrants who threw rocks and tried to cross the border between Belarus and the EU.
The clashes come as the EU prepare to impose further sanctions on Belarus, which it accuses of attempting to destabilise the bloc by pushing hundreds of refugees across the border illegally.
Footage shared by Polish authorities showed more than a dozen men firing projectiles near the border crossing at the north-eastern Polish town of Kuznica.
Migrants can be seen throwing bottles and wooden logs at Polish troops and using sticks to try to break through a fence.
Poland's Interior Ministry said a policeman was receiving treatment for a suspected fractured skull.
"Migrants attacked our soldiers and officers with rocks and are trying to destroy the fence and cross into Poland," the Defence Ministry said.
"Our forces used tear gas to quell the migrants' aggression."
The EU has accused Belarus of encouraging migrants to cross the border after the bloc imposed sanctions on the country owing to a crackdown on protests against President Alexander Lukashenko's re-election victory.
"We cannot let this so-called problem lead to heated confrontation," Mr Lukashenko told a government meeting, state news agency Belta reported.
"The main thing now is to protect our country and our people, and not to allow clashes."
Belarus migrant crisis - in pictures
German Chancellor Angela Merkel held talks with Mr Lukashenko on Monday and they discussed allowing the migrants to receive humanitarian aid. Many of the migrants are young children.
It was the first time Mr Lukashenko spoke to a western leader following last year's protests.
"We were of the united opinion that nobody needs escalation – not the EU, or Belarus," Mr Lukashenko said.
But he said their views differed on how the migrants got to Belarus, with the West saying Minsk brought them there as revenge for sanctions.
French President Emmanuel Macron and Russian President Vladimir Putin agreed on the need for a de-escalation of the crisis, even if the two leaders disagreed on its origins, a French official said.
"The goal of this call was to put an end to this crisis," a French adviser said.
Mr Macron spoke to Mr Putin for an hour and 45 minutes.
"On the migration issue, even if there's no convergence on the origins of the current crisis at the Belarus border, Vladimir Putin told the president he understood the need to put an end to it, first and foremost out of human decency for the migrants that are being instrumentalised," the adviser said.
Images of migrants gathering at the Belarusian borders with Poland and Lithuania also prompted a no-confidence motion against the Finland government more than 800 kilometres away.
Opposition MPs filed a no-confidence motion against Prime Minister Sanna Marin’s coalition government on Tuesday over claims the country is inadequately prepared to deal with a flow of migrants across its 1,300-kilometre border with Russia.
In 2015, more than 30,000 people from Asia and the Middle East arrived at the border seeking asylum. Officials blamed the surge on Moscow.
The Finnish opposition proposed adding a clause to legislation that would allow the government to stop accepting asylum applications in case of mass entry to protect national security.
No-confidence motions are a common way to force debate in the Finnish parliament, with Ms Marin’s government already overcoming seven votes since taking power less than two years ago.
