God Leobin did that when he was sick with an ear infection AND teething at 5 months! He bit so bad he drew blood which poured out. blurgh
It was so stressful for me, have to say, like putting your nipple into a vice and hoping for a good ending! But it definitely did pass! Now he seems really gentle.
'yelping' when he bit didn't work for him (which I did out of sheer shock!), he was so upset and cried and refused to feed. Took a good few days to get him back to eating.
Now I want a chocolate biscuit.