What to do when the man who made me fall in love wants to stay single until he's healed and happy on his own?

Ask sincerely if you're the one he wants to try with when he's healed, and be there for him as a friend until then but not so much as a kiss on the lips until he's romantically available

Hugs are fine though

All you can do is give him the space he needs.

He ever wanted or said he wanted a relation with you?
Did the way he made you fall in love with was just a casual thing that happen, or was he trying to do it?
And if he wants be single it is choice, and you should let him be,

If he loves you enough, he will do anything you want and after a reasonable lenth of time and he still won't marry you.
either resign to his wishes or move on ❤️

Respect his mental health