Worry about it!
Put some ibuprofen gel on it and if it is not back to normal within 24 hours, GO AND SEE a doctor.
I would seriously consider changing dojo. As nage, one has the responsibility not to hurt uke. It may have been a mistake and those do happen but if this is a regular thing at your dojo there is a problem... Or at least I think there is a problem. If you're doing to "angry white pajamas" training then expect it.