"Do I need to go back to the emergency room? The pharmacist had told me it would take 1-2 days before feeling any effects... it will be 2 days on Monday evening."

It is recommended to wait 48 to 72 hours after starting antibiotics to properly evaluate their effects. If there has been no improvement in swelling, redness, or pain after this time, it may be necessary to return to the doctor for further evaluation.