A numb lip is a sign of way too much mouthpiece to lip pressure.
If the CAUSE is taken care of then it may go away. It could take months for the feeling to return. If enough damage is done to the lip the feeling will never return.
Continued abuse will also damage more than the nerves. It will injure the muscles and not only affect playing but also appearance and speech.
This is VERY IMPORTANT. The mouthpiece to lip pressure has to stop TODAY !!!
I would suggest a month off of the horn. Hopefully the feeling will return in this time. Horse flapping (a loose buzz) will help.
If playing is to resume after a month off then I suggest lip buzzing. Lip buzzing (NO MOUTHPIECE) will teach a close embouchure setting and increase lip strength. This will make it easier to break the mouthpiece pressure that has been used as a substitute for a closed lip aperture.
I wish you the best of luck. Also please email me after being off the horn for a few weeks. We can then see how much damage there is and start some exercises to help. Do the buzzing.