1994 Other Peugeot Models sruggling brakes after rear left w

Brakes problem
1994 Other Peugeot Models Manual 55000 miles

Hi recently I was parked up in a muddy field and when trying to leave ended up having to be pushed out as wheel just kept spinning and getting no tranction. Once on the road if became apparent that the rear left wheel had locked straight and wasnt turning. After a few times of reversing and then driving forward it eventually began turning again. However now the brakes on the car are struggling with the brake pedal going all the way to the floor and only gradually slowing down. It also feels like when I brake the car is going to one side slightly.
Anyone know what might have happened i'm a student and have hardly any knowledge of cars but do you think it will be an expensive job getting fixed? Any help would be appreciated, thanks