Robroy, what you have is called phimosis. The "ring" you describe is a muscle that exists at the end of a normal foreskin but in your case it is very short and quite rigid. It is not a "bone thing"
Although stretching works for some guys (and it sounds like you have had some success with it already) for some it does not completely solve the problem. Repeated stretching or over-zealous sexual activity may lead to tears developing in the foreskin which, when healed, may cause it to become even tighter.
Being able to retract ones foreskin on a daily basis is very important in maintaining proper penile hygiene. For guys who have normal foreskins, this is a very easy process, but I am sure that because it is so difficult for you, you probably don't do it nearly as often as you should. Behind what is called the corona of the glans, there is a groove into which smegma can be deposited. Smegma is a combination of dead skin cells and mucous that your inner foreskin naturally secretes and is in itself harmless. But when it is allowed to remain on you penis for prolonged periods, it can become infected causing you more serious problems. It also smells quite unpleasant and can be offputting to a sexual partner.
For someone in your situation, circumcision would be a one-off, permanant solution to the problem. It is not a disaster as many on the Internet like to describe it. Millions of men live very happily without their foreskins and as yours is abnormal, I would say you (and your sexual partners) would certainly benefit from its removal.
By all means, continue with the stretching, but be aware that there is an alternative which would fix your probelm forever.