Nope you don't need AC service. If it smells like urine, you have mold and or mildew growing in your AC evaporator. Sometimes the AC condensation drip pan does not empty completely making it a perfect place to grow mold and mildew. Best way to eliminate mold and mildew is with an ozone machine. It will kill everything living inside your vehicle. Most water extraction companies can assist you with this. Good ozone machines are expensive.
Or go to the dealer or a good detail shop, they have sprays which are injected into the vents and this kills the top layer of mold and mildew. But make sure someone looks into your condensation drip pan to make sure it is not clogged.
Then finally soak a clean towel in white vinegar, place it in a bowl or pan and set it on the passenger floorboard, close the doors and windows. The white vinegar fumes will eliminate any lingering odors. After a few hours remove the vinegar soaked towel, air out the interior and you will have an almost new smell to you interior.
This works great to eliminate cigar and cigarette smell too.
Hope this helps.