Hi, I've no experience on this and had to look up what PIRADS is, and 3 is indeterminate. Your psa is low. Having read your profile I'm not sure why you had the MRI and are being monitored.
At first thinking it appears a case of you got so far and now feel pressure to carry on even if it isn't needed. That's quite common. It's also common to look for changes if things are indeterminate.
Psa can be inconclusive, so can a biopsy. Some people have no psa reaction and that's a risk. Also some can't take the stress of not knowing.
I thought about this and decided that if I kept waking at night worrying, I'd have a biopsy. To be honest having got on this treadmill I'm sure I'd need the biopsy even while thinking it won't be me. That's just me hopefully others will give their opinion. All the best Peter