Don't jump to the worst conclusion. It doesn't sound serious. If the sensation continues, have an examination by a dentist or an oral surgeon.
to me, as a dentist, it does not sound like it is related to cancer at all. relax, and see a dentist or oral surgeon if it persists.
Sounds like the numbness is right across your lips - in which case nerves from BOTH sides of your body would have to be affected and therefor you would need to have symmetrical tumours grosing in exactly the same place on both sides of your body. THIS DOES NOT HAPPEN. You dont get simultaneous and symetrical tumours.
Pervious advice is good - however if your symptoms do not improve or get worse then consult your dentist / doctor and there could be a reason you are getting an altered sensation.
have TMJ
anxiety,
tingly area would move to different locations
little bit of post nasal drip and sinus pressure
These sound like hypothyroid symptoms to me. Have you been tested? If so, get your own copy of blood test and double check levels. Most lab ranges are out of date and docs do not realise. Also suggest get thyroid antibodies checked.
Also...check B12 which is common in hypoT sufferers. This can be culprit for numb lips and nose etc IMO.
A related discussion,
Tingling sensation in lips. was started.