Go out to trail and hand walk him there. Treats, cuddles, and kisses are the best thing for a pony that has been in the stall for so long (at least that's what I believe). Try to use this time as a bonding time for you and your horse. Give him a good pamper (ie: grooming, bath him) and use the time to your advantage. You can deep clean all your tack, get to know your horse better, and a lot more!
I wish you the best of luck with your pony and I hope I helped!