Shall I enforce HOA and Pet violation fines mentioned in lease?

[Manny K.]

Rented out a condo 3 months ago. Tenant turns out to be a chronic liar/rule breaker. Second month's rent was late (eventually paid with late fee only AFTER I served a notice). A pet dog was found while I was there to serve pay-or-quit notice. Lease says NO Pets - and I can fine $150 per pet violation incident. I served another "cure-or-quit" notice -- BUT let him away with a warning (instead of fine) and promise to remove dog within 7 days. He claimed dog is gone and I didnt see it when I visited again. NOW, last week HOA sent a letter saying tenant is walking dog without leash and neighbor complained of late night noise/nuisance. Lease allows for $50 "fine" each time landlord has to be involved in resolving HOA violations and also allows for pass-through of any HOA fines. So, the question is -- what is the best strategy to enforce and resolve such issues? Send a notice and actually enforce the $150 pet violation and $50 HOA violation fines? I feel soft "warnings" do not mean much with this tenant. What happens if tenant denies any wrong-doing... or ignores/refuses to pay (asking for proof etc)?