Mon., Wed., and Fri.
Squat 2x15 (No weight, keep both feet flat on the floor.)
Push-up 2x15 (On your toes, go until the chest almost touches the floor.)
Lunge 2x15 (Alternate legs, 1 rep left/1 rep right.)
Neutral-grip pull-up 2x15 (assisted if necessary. Could be substituted with inverted rows.)
Plank 2x15-count (Hold the top part of a push-up, on the toes, arms straight, keep the whole body straight. Count to 15.)
Burpee/squat thrust 2x15
As soon as that workout is "easy" (could take one week, could take six weeks, doesn't matter), there are any number of free weight-focused programs you can start on.
Building a foundation with bodyweight exercise will build conditioning and strength while helping to prevent any future injuries. Even if you have some experience with weights, I'd just on this plan for a week or so, just to see where you stack up.
So you're looking to gain size. No problem. As others said, that has to do with what you eat, not so much how you train.
What, exactly, did you eat yesterday?