Really really really sore nipple

I've developed a really sore nipple/areola over the last day or so.  It initially felt as though he'd just kneaded a bit too hard with those sharp little teeth of his but I would have noticed if he'd bit me, it's only on one side and it's getting worse not better.

It hurts all the time but especially when he feeds off that side and feels kind of like a nipple bleb except I've checked my nipple and there is no little blister.  I've wondered each time he feeds off that side whether he will draw a block closer to the surface but no joy.  I have no lumps that would suggest a blocked duct or mastitis and the pain is really focussed in my areola and nipple. 

Any ideas what this might be?  More importantly any ideas to fix it would be greatly appreciated. 

I'll continue to feed through the pain but I'd rather feed without pain if at all possible.

Thanks so much ladies. 

Thrush hadn't even occured to me but since you mentioned it I went to my docs and they said that although they can't see any signs of thrush it definitely sounds like the start of an infection and prescribed me ab tablets, they didn't see the point in waiting for it to get worse just so they could 'see' it and after 10 months of feeding there was not even a suggestion that he may be latching wrong. 

I'm so relieved that it is something easily solved.  Thanks again.

Good point SquishysMum.  Something didn't seem right there but I couldn't quite figure out what

The doctor said the abs were to treat an infection, they didn't say which type (I just assumed thrush because that's what I suggested it may be) so I'm guessing that they think I've got early stages of mastitis.  I'll ring them in the morning to clarify.

Thanks again.