This persistent abscess which does not clear with antibiotics is called Parulis as this elevated nodule is actually an opening of fistulous tract from some chronic abscess either in association with tooth (periapical abscess) or gum abscess or could be sinus in your case.
As I can not do physical exam hence can not say for sure about the origin of the abscess. It needs x-ray and second opinion of a dentist who can examine.
I cannot remember to ask everything at the same time. I have had a CT scan and no fistula showed on this, no infection. The swelling on the gumline is at least an inch long over where the missing tooth is. This was also packed with graft material as the post was removed at same time as lift was done. I never take this long to heal and this has been very slow and painful. The pain and congestion are finally manageable and the swelling is smaller than one month ago. The area beside my nostril remains tender from time to time. Thank you for any further help.
The points raised in this message are going into the favour of healing area as the symptoms are reducing. This reduced swelling could just be healing callus as mentioned in another message. Do not worry as stress delays healing too. Grafts may take healing time of about 6 months for complete bony recovery. Take care.
Thank you for your comments and advice re the xrays. Yesterday the "abscess" was a bit more sore as well as the sinus. This seems to be the pattern - a few days feeling like it is healing and then a day of discomfort. This morning I have a bit more congestion which usually recedes as the morning goes by. There seems to be a stiff feeling around the whole site and then I can have a meal and the warm food and movement seem to loosen it up. This is all very disconcerting. Any further thoughts?
Is the fact that the sinus and swelling are sore occasionally something to worry about or will nature heal? It has been 4 months. Thank you again.
Wondering if the issues I have mentioned need to be addressed ASAP. Reason I ak is that my father has taken I'll and I must be away for a few weeks. Thank you.