Was it a contraction?
Hi I get these really bad pains, and they really hurt, but as my mum has had 3 children she knows what a contraction feels like and she said it wont be a contraction as they normally start across your stomach and not in one area like on your side plus they feel like period pains and just get worse then your tummy feels like is tightening. Its proabably you baby engaging down and lying on a nerve and you body just preparing for labour. But if they get really bad then phone your midwife and ask her thats what they are there for.