Turn Signal problem on 93 Chevy Lumina

My girlfriend's Lumina is having some issues. Someone backed into her car a couple of weeks back, and destroyed the tail light. I replaced it with a new one as best I could, but some bent metal kept the light cover from fitting perfectly back into place. The left turn signal worked fine at this point. About a week later, we had a big storm roll through, and suddenly the turn signal stopped blinking. It started back working again later that day, then had stopped again by the next morning, and is still broken 4 days later. It lights up when brakes are applied, but won't flash. The right turn signal works correctly. Is this a fuse issue? New bulb? Can anyone help?