don't think its super smart to do uber heavy before you get man tendon strength as these injuries will continue to happen. esp when your growing or JUUUST finishing growing your tendons are stretched and not strong same as ligaments muscles etc. time after time ive seen this in high school and buddies kept lasting injuries into 30s some getting surgery most of the time surgery just made thing worse as weren't debilitating just would be sore when used.
anyway, best thing is to go to PT to get on strengthening the tendons after a few weeks of healing.. does it click or grind? they are also about 90% better than docs at diagnosing soft tissue stuff. esp if get a good one, stay away from PT who are Chiro or work with Chiro s too closely.. esp if can get a pediatric PT that would be best as can grill them for best practice for kids as shouldn't be doing adult stuff just yet esp without perfect technique.. IMO at least. I do think weight is important as best time to build ur structure/bones when young, again just in my opinion as makes sense to me. it also is best time to garner lasting issues it seems, me it was my knees, thought I was so cool doing full racks on leg machines, cut to dislocations and same injury as your son with knee caps. they crack and creak not only can u feel it folks walking down the stairs near me are like dam ur knees are loud lol.. fortunately dont hurt very bad but im sure its coming when start getting arthritic.
id say stay away from too much alleve, shits not super for ur kidneys, if can avoid it. omegas and baby asprin

unless cannot move without alleve. also anti inflamatory creams dunno if can get good stuff in USA but can be helpful targeting inflamation.. if need to even just 1 pill am or pm, pm being slightly more ideal IMO as during healing at night.. hot cold creams IMO are good first line for kids, or some Cbd creams maybe, some people find them helpful and very least great placebo for a teenager, although now days perhaps different, when I was young hemp seeds and hemp necklaces were the coolest as were weed but now less forbidden... perhaps some cucurmin with the omegas. imagine have him on some quality multi source proteins. my feeling is that whole beast protein powder may be good for healing, never looked at the label but seems like would have lots of minerals and aminos/collegen vitamins like d A B and E. and being food based and not artificial B vitamins like 99% of supplements my feeling is they are superior.
anyhoo, go to PT or can google up some elastic workouts online after several weeks. but a good PT is a great resource to ask questions get proper techniques etc. they also have fun tools to reduce inflamation