Thank you for your query.
At this age children do put every thing in the mouth. It is quite possible that your son might have hurt himself around the mouth and the right eye while trying to put things in his mouth. As I have not examined him it is difficult to give a reason. Other possible cause(s) are insect bites
, etc. Since there is not other problem I would suggest that you can wait and watch. In case they increase in size or number, you need to consult a doctor.
I hope I have answered your query to your satisfaction.
Wishing your son all the best.