You could try the method mentioned in the link below. You can also try one which I've recently heard of which may be successful.
It's a bit difficult to explain but here goes.
You need some very thin chord.
Poke a short tale of the chord under the ring TOWARDS the wrist leaving a long length trailing towards the fingernail. It may be easier to do this on the palm-side of the finger where you may get a bit more movement.
Now you need to wind the long chord tail round and round the finger as tightly as you can bear on the fingernail side of the ring. This has the effect of compressing the finger, and is obviously easier if you have someone to do it for you. Continue until the chord goes right over the knuckle.
Next, you take the short tail and pull gently in a winding motion, this makes the ring move up over the tightly wound chord and eventually over the knuckle.
Give this a try, but if it doesn't look like it's going to work, follow my advice in the link below, do not wait too long before making your mind up.
http://www.theanswerbank.co.uk/Body-and-Soul/Q uestion244013.html