Small screen on top left after game ended

Ever since my game froze and reseted my computer, my game became small and ended up on the top left corner once the match was over. I wanted to play again but since the screen got smaller, I couldn't see anything or even leave the game. I tried clicking alt-enter but it still doesn't work. The only way I can play another is by resetting my computer and logging back on. Someone pls help me with this problem.