Hi Paul
Unfortunately it sounds like your chances of being able to claim are unlikely. Limiation for a personal injury claim is 3 years from the date of the accident. NOT unfortunately date of discovery of the injury/problem.
In order to claim you would also have had to have reported the accident and you injuries to the hospital or Dr at the time or within at least 6 weeks or so of the accident.
If your accident was within 3 years and was reported to the hospital or Dr at the time then you may be ok and obviously could look to claim. The easiest way to check the date of the accident if you did visit a medical prectitioner is to simply ask them to consider your medical records and this will give you a very clear idea.
Hope this helps.