Mrs Jacob is 30 weeks pregnant and has requested an emergency appointment as she has a painful finger. She initially noticed a small area of erythema at the top end of her nail (right fourth finger) three days ago. Since then it has become painful and swollen. Last week she had a manicure but has not had any trauma to the area. She is systematically well. She has no significant past medical history, is on no regular medications and is allergic to Penicillin. On examination, there is a well circumscribed area of erythema and swelling proximal to the 4th right fingernail base that is tender to touch but with no obvious collection.
Given the likely diagnosis, what is the most appropriate treatment?