Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns..
As per your complain a lump on the gum at the site of infected or decayed tooth can be due to abscess formation due to pus accumulation at near the root tips of infected tooth which gets accumulated into the soft tissues causing swelling..
Although at times the tooth can be painless as the decay must have caused
necrosis of nerves and blood vessels making tooth non vital but pus below the root tips can cause pressure on nerves leading to pain..
As it seems to be a
dental abscess, you need to get back to your
dentist and your dentist and get evaluated and he can advise you a course of antibiotics like
Augmentin and also advise you anti inflammatory painkiller like
Ibuprofen..
You can also apply a numbing gel over the lump for pain relief..
This will give you temporary relief, but to attain permanent relief, you need to get
root canal treatment of the tooth done followed by a course of antibiotics and painkillers..
Hope this information helps..
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Thanks and regards..
Dr.Honey Nandwani Arora.