Baby gum looks black/bruised???

DS2 (8 months) appears to be teething. Lots of drool, a bit more unsettled and his gums top-centre have been bulging for a few days. I had a look this morning to see if anything's come through and noticed that on one side, the bulgy bit is quite blackened. As if the tooth that is behind the gum is black or at least the tissue is very bruised. It's freaking me out a bit. Never seen this before.

I'm worried that in one of his many, many stacks in the past few weeks he's managed to damage the tooth (though I can't think of any that were specific to this area). Has anyone seen this before?

Sounds like an eruption cyst, it will go once the tooth is through and isn't anything to worry about
Xxx

'Eruption cyst'?! Great name! Thanks. Freak-out over.

Lol !!