Ay, madalas talaga yan sa babies, lalo na kung suminusubok na sila ng lahat at nag-explore ng mouth nila! But honestly, better to check with your pedia just to be sure kung ano exactly yung spot na yan, could be thrush, or maybe bite mark lang from teething toys, or something harmless. One of my mum friends had the same concern at 4 months, and turned out normal lang, pero good na na-check pa rin agad to rule out any infection.