Thanks for your query.Based on the facts that you have posted it appears that you have urethral diverticulum.
If you do not have symptoms like driblling micturition, burning urination or have mild symptoms you can just take antibiotics and anti cholinergic drugs.
However if your symptoms are severe enough to disrupt quality of life you need to get surgery done.
Please consult qualified Urologist
for detail assessment and further treatment.