Your overall risk isn't significantly high, but it's a risk none the less. The decision to seek out PEP would be a personal one, and one you'd have to discuss with a doctor, to weigh the benefits vs the risks. You're correct that PEP must be started within 72 hours of the exposure, and the sooner, the better.
Typically, PEP is reserved for people who have had an exposure with a KNOWN + person, but again, it's your call. I can understand the worry and the desire to take precautions.
The chance is low but I would get PEP if possible.
1. Not in your situation, but it's still a personal decision after speaking to a Dr.
2. It was a risk
28 day DUO test or 6-8 week antibody test will give you a good indication but 3 month antibody test is conclusive.