Ok thanks for the helpful advise. Well see how it goes over night and possibly visit a vet tomorrow. He had flea treatment about 3 weeks ago. Hasn't been out on grass yet as only had 2nd vaccination 4 days ago ( this could have something to do with it)

Really hope he's ok, let us know how he gets on

Oh bless no wonder you are so worried - I didn't realise he was quite so 'new'. I suppose it could be a reaction but it seems a bit after the event for it to take 4 days to appear but then what do I know?

As Eileen said - do try to let us know how you get on.