Is this a sports injury?

Help,

3 months or so ago I started back at the gym on aerobic training or the bike and concept 2 rower, after a 2 year break, needed to lose some weight.

Ever since I have had a pain, and a slight protusion on the bone (presumable where the pattella ligament joins the bone) at the top of my shin bone (tibba?) under my left knee. If I try and stretch my thigh by lifting my lower leg the pain becomes intense above 90%.

I thought it might be the bike or rower, so I stopped that and took up running (legs don’t bend as much), still hasn’t gone, so reduced down to walking the treadmill, still hasn’t changed.

I have read a few other posts and didn’t recognise this as being teh same as most of the knee problems.

Clearly it is getting to the time I should see some one, however I would like to know what the possibilities are, after all I’ll need to get past a GP before getting anywhere near a specialist.