2days ago my 10momth old was prescribed amoxicillin for ear infection today I noticed a rash on the sides of his face. Should I be concerned?

No. If the rash is getting worse or is raised like hives it is a reaction to the medication and it should be stopped. If he had a fever for 3 days prior to that and now the rash it is likely a viral infection called roseola and is unrelated to the the medication.
Maybe,maybe not . Rashes occur often in kids and some can be related to antibiotic use. A localized rash, is less likely triggered by ingested antibiotics and more likely a local contact dermatitis. If it spreads to other areas, has a raised nature or a purplish color, it could be the antibiotic and stopping would be appropriate. If it stays in one location, monitor until you can contact the kids doc and discuss it.
Call Pediatrician. Pediatrician should be notified immediately. Could be from the bacteria that's responsible to the ear infection. Could be allergic response to the amoxicillin. Call pediatrician now.