Thanks for sharing your concern.
The cause for your present symptoms appears to be involvement of your molar adjacent to your implant.have you got that checked thorughly?
As you have mentioned that your dentist
says the implant is free from infection,that means the adjacent teeth in that arch is infected.
This is sure that infection is there as your lymph
nodes are palpable and indicating infection.
It is also possible the pain could be due to enamel wear.the underlying dentin
is getting exposed to noxious stimuli and further affecting pulp and causing pain.
In this case i would say please revisit your dentist and get it examined thoroughly for the exact cause of this pain and infection.
Only clinical evaluation with clinical tests can elicit the cause for pain here.
Meanwhile please mange with pain killers till you visit your dentist.
Its very nice to know that you are maintaing good oral health.
Do not worry it will be fine.