I don't have any specific advice on the tendon issue since i know nothing about that (only thing I do know is those plantar fascietis (sp) injuries that can take forever to heal).
What I woudl advise is to be very careful about dismissing a "minor" injury, because I did that, and now I'm paying for it by not being able to run for the rest of my life.
I had what I thought was a minor injury in my knee once, and while it was painful it was not too bad, and I jsut gave my leg some rest and then slowly startedd up my running again. Other than the occasional tight feeling, it was fine. Year and half later, it turned out that I had in fact torn my cartiledge, and if I had seen a doctor at the time, it would have been a simple ortascopic operation - and I could have run marathons still. Because I thought it was okay, and ran for 18 months on it, I screwed it up so badly, that I was told never to run again, had surgery last summer - and now am getting ready for another round of more serious surgery. All because I didn't see a doctor up front, and assumed it was okay because it felt better.
I'm of course NOT saying that anything like that is going on with you - but I just wanted to share then sentiment that sometimes it really is much better to be safe than sorry.
If it's all coming out of your own pocket, Id' definitely skip the GP and see a specialist first (IF you go, of course). If it is out of your own pocket, try to negotiate up front for the cost of the visit - you can often negotiate a lower rate than what they charge an insurance carrier.
Sorry that I've only got no specific advice. Hope it's nothing seriuos and that you'll be fine without having to spend anything.