Sporadic and painless blood in the urine?

I've been noticing a little bit of blood in my urine lately... but I am not in any pain, nor do I find it difficult to pee. Should I be concerned? It only started happening about midway through a course of antibiotics I had for a tooth abscess. I had the drugs Amoxicillin and Metronidazole 3 times a day for a week. I have only been off the drugs for a few days but I read somewhere that some antibiotics can cause urine discoloration and blood in the urine so I decided I would wait until I finished the drugs. But the blood is still appearing (sometimes), it's only been about two or three days since I had my last tablet, should I be concerned?