Did you have any hip or buttocks area pain before you went to the chiropractor? If so, it could be from that, as pain in those areas of the hip can be felt in the groin. I don't understand why he would put his full body weight on your legs, but there is an adjustment they do that involves the lower part of the back where they work on that area. I'm not aware of any expertise they would have if the pain was truly isolated to the thigh unless he though that pain was coming from your hips or lower back. If it was isolated to the thigh, some sort of massage might be appropriate for temporary relief, but chiropractors really do only study how to adjust the spine. They can and do learn all sorts of other things as can any medical practitioner, but again, if you just strained your thigh somehow that would probably go away on its own but it's hard to see what special talents a typical chiropractor would have for that. Nobody can tell you if a nerve was pinched, unfortunately. There is a test for it a neurologist does, but it misses more than it hits. I think it's called an EMG. I don't know what a regular doc could do for you, as diagnostics would be required and usually you'd be referred to a neurologist if it's nerve pain only or an orthopedic surgeon if structural problems such as the hip or the back are suspected to be the cause. It it truly was caused by the chiropractor, I would think it would go away but since it hasn't, you're right, something is up.
This may not answer your direct question but it’s information. Can never have too much. I see my chiropractor regularly which is to say when I think I need it. Took me a while to find one that was on the same wave length as me but now I’m good. Anyway, when I first went to him I sheepishly told him that my testicles sometimes hurt when my back was also bothering me. He calmly advised that it was very common for the symptoms I described. So, at least in my experience, pain in the groin area was treatable by chiropractic. Tell your chiropractor what’s bothering you and maybe he can help you. Good luck