Hello mate.
A warm welcome to you. I'm sorry you've needed to find us but glad you have.
Your prostate seems large, probably double the normal size of a man your age. There can be many prostate conditions that cause this enlargement and that could also account for your slightly high PSA.
To be on the safe side I'd be guided by your urologist, if he thinks a biopsy is appropriate, then perhaps it would be wise to follow his advice.
I believe PI RADS 4 means that the lesion is likely to be cancerous, so a biopsy would clarify your condition.