Player keeps sticking to walls

I’m making a simple 2d sandbox game, and when you place a block and run into it you can stick to it if you keep applying force to that direction. I have tried adding a physics material to all the blocks in the world, but that just makes the world become extremely laggy.

I had this issue with my game as well (3D game) the issue was with the character controller. Try increasing the skin width.

What is skin width exactly, and how could I change it?