I went to the emergency dentist after several days of pain in a root-filled tooth on Monday. X-ray found I have a periapical lesion and I was given the option of extraction or a year on the NHS waiting list for a new root canal treatment (with not great chances of success as the tooth is already very deeply filled and quite fragile). I opted for extraction. In the meantime, amoxicillin has helped the pain subside massively in the last 48 hours.
I'm slightly scared about the extraction though - which is TOMORROW. More precisely, the chances of a piece of infected root staying in there, and the chance of infection. Any tips/experience to reassure me?
Also, the dentist said periapical lesions are commonly asymptomatic unless there is a secondary infection, which can happen because of low immunity. This concerns me as I don't have any health conditions that I know of, haven't even had a cold for more than a year, and have a healthy diet. As far as I know, my only health condition is hypochondria. 
Should I be worried there is something more sinister going on?
Please go ahead and tell me I'm being ridiculous.