Fiona's back gets sore if I ride bareback after a long hiatus of no riding. She has always been sensitive. I do plan on treating her to a massage therapist for her birthday though, lol.
Your best bet could be a chiro or a massage therapist. It can be as simple as what your dad said, though.
Horses went without message therapists and chiro specialists for decades. We do want our horses to be as comfortable as possible, but it really only takes one ride, one roll, one bad turn, to reverse the money invested into those services.
You said you put a saddle on him, are you confident it fits?
The Fluffy Equestrian
Rhett | Hang on "Fiona" | Rockstar
Reg. TWH Gelding | Irish Draught Horse Mare | SSH Gelding