<s>[INST] Just within the past 4 days I started to feel a hard lump. Its located in the rear of my mouth inn the gum, just below a back molar. center area. I have a rabbit of brushing my teeth really hard. It seems maybe that caused it. Anyhow it s sore but definitely a bone like lump that just seemed like it popped up over night. [/INST] Thanks for your query, I have gone through your query.The hard lump could be a periapical abscess or a cyst secondary to tooth infection.Consult a oral physician and get a radiograph done to rule out these things. If it is a periapical cyst and granuloma then get the tooth treated with RCT or extraction of the tooth. Mean while you can take a course of antibiotics like amoxicillin 500mg and metronidazole 400mg tid for 5 days (if you are not allergic). Do saline gargling. I hope my answer will help you, take care. </s>