As usual, Pat is right on. A positive PPD without signs of active tuberculosis (no symptoms [night seats, weight loss, cough] and negative chest x-ray) is latent TB. The treatment with isoniazid (INH) for 6-9 months is aimed at preventing reactivation TB later in life.
To the best of my knowledge BCG does not increase the risk of developing reactivation TB. In fact, BCG is used as an immunzation against TB in areas outside the US where TB is more prevalent.
In addition, I don't think the PPD would be a reliable way to decide if the BCG is causing a problem, since the decision must be made on the basis of symptoms. A negative PPD would not be adequate to decide that the BCG wasn't causing a problem if one was suspected.
Even though you need your urologist for his expertise treating the cancer, you need him to consult with an infectious disease specialist, who you should consult with as well. Then your concerns will be accurately addressed and an appropriate TEAM will be making the decisions. Don't forget, you're a member of that TEAM, so you need accurate information to make your decisions