Occasionally a blood vessel in my lower leg ruptures & it stings, a lump forms that is very painful to the touch & appearance of a bruise.?

Question?: Not sure what the question is you are asking. However, this can happen. Doesn't necessarily mean anything bad but it can certainly hurt. You may need to consider some type of compression socks/hose.

Varicose veins: This sounds like a varicose vein that has ruptured. You need to have an evaluation by a vascular specialist. This should be treated as the bleeding and ulceration can be a chronic problem.