Vertical Pink bands-Nails. Could be?

Hello Doctors, I noticed these Vertical light pink bands on middle finger nail plate of my left hand about 1mm. On a closer look, it is seen in every finger's nail plate. If I press my nails, this band disappears. Is it a normal occurrence or is it something serious? I haven't noticed this till recently though. I'm scared if this is melanoma, as per the information from internet. The growing while nails in the free tip also appears to be little shaded as well due to this band and it grows in the same shaded colour once it regrows. I tried cutting the nail plate a bit deeper and could see that this band is NOT present on skin but only on the nail plate. Could you please advise what this could be? Any infection or something really that I need to be worried about. I had all my medical examination about 5 months ago and all came out to be normal.