Are genetal mollescum contagious a week after liquid nitrogen has been applied? also, can the virus be active under the scab that forms?

Still contagious: Molluscum contagiosum lesions probably are infectious unitl healing is complete and at least a couple of weeks have gone by without appearance of new lesions. For example, if you have genital area molluscum (the usual site at your age), you shouldn't be having sex for at least 2-3 weeks, maybe longer. (But no problem with a partner who already has it, for example whoever you caught it from.)