I’ve had tennis elbow and golfers elbow in both elbows. Those conditions can take a very long time (6-12 months) to heal with just conservative treatment like stretching and rest.
I don’t have direct experience with PRP treatment, but even if it accelerates recovery, I’d imagine it will still take a long time, and you’ll still need to treat conservatively (stretching and rest).
The two things that have worked for me are 1. stretching (religiously, multiple times a day, every day) and 2. For tennis elbow (outside of the elbow) an arm brace.
You can look up the best stretches on YouTube. Eg:
Brace