Any increase in PSA is worth looking in to.
There are various activities that can cause a temporary ride, a blow to the groin area, riding a bike, having ejaculated within 48 hours of the test, infections and others that I can not recall?
There are ranges for ages where your PSA might rest, but these are not prescriptive, so you may be an exception either way?
At age 56 I had PSA 5.5, which rose to 6.4 in 6 weeks. I was diagnosed, thought to be an aggressive cancer, and had it out. The rate of increase may indicate whether or not you have a pussycat or tiger PCa, if you have it at all, see the various activities that can cause a blip above.
Without further exploration you can not know? IIWM I would see my GP again, and arrange a PSA test, and refrain from any of the activities listed for 48 hours prior to the test.
Good luck.
Dave