My left breast is numb after explant, is this normal?

Some numbness may certainly occur (normal) after the procedure you have had performed; most often temporary but possibly permanent. Best wishes for an outcome that you will be very pleased with.

hello sophie143  Regeneration of the sensory nerves is accompanied by tingling, burning, or shooting pains which disappear with time and are nothing to be alarmed about. If, however, swelling, redness, infection, or drainage accompanies this, then you will need to see the doctor at the office.

Numbness isn't uncommon after surgery due to the trauma to the nerves from the procedure.  Many times it resolves over time.  I encourage you to speak to your surgeon about your concerns as he/she is most familiar with the details of your surgery.