This question is not as easy as it sounds.
The obvious answer is to see a Urologist who will inevitably advice a biopsy and proceed from there ........whatever the biopsy showed...malignant or benign.
However...if it were me:
If it was me, aged 80, with a poor medical history and a normal PSA ( blood test for prostate cancer) then i would ask the GP to do nothing and repeat the PSA in 4 months. If it was still normal, then monitor the situation, but if it was rising, then ask for a Urological opinion and biopsy.
Discuss this with your GP who will have your PSA results and know your symptoms and will put forward the pros and cons of "doing nothing."