My two top suggestions would be
1. Linda Tellington-Jones body work (books available at libraries or stores and she has a website)
2. Clicker training – backing, vertical & lateral flexion, side passing, lowering head, accepting bit, head down, pick up feet, etc. Lots of books available on what/how/when to use clicker training.
My mare loved to use her hoof to play a child’s toy piano, blow into toy musical instruments, and play with jingle bells on a hay string. She liked to push a ball with her nose back to me, or lightly nudge a ball to me.
And the usual suggestions:
Try feeding smaller meals more frequently – several hay nets safely placed or slow feeder (wooden box type)
Central stall so your horse can be (see) in the middle of barn activities – open door & put up escape guard so he can really hang out with you
More grooming time
Jolly ball, tether balls, hanging stuffed toys (if your horse won’t tear them apart)
Jug tied up safely so they can nose it and dispense their own horse treats or grain
Baby rings on a rubber stall guard to push back and forth
Himalayan Rock Salt on a rope
Cut up favorite fruits and vegetables and hide them in the hay
Horse safe mirror
Hope he heals well! Have fun and enjoy the extra time you get to spend with him.