Focus on the basics, 1-2 exercises per session. You won't be able to grow muscle but you will be able to save most of what you have with something like this ...
Day 1 - Squat, Press/Close-grip bench
Day 2 - Deadlift, Chin/Row
Day 3 - Dip/Bench, Curl
Keep the weights heavy-ish (5x3 or 5x5 or perhaps 3x8 protocol but no lighter).