Hi, although the x-ray is not very clear, it appears there is a cavity in both the 1st and 2nd molar teeth at the area of contact. You need to follow up and consult with your dentist for the appropriate treatment if a simple filling will suffice or a root canal treatment is required. In any case a further delay should be avoided as when the decay starts then it spreads fast and since a decay softens the tooth, the tooth can crumble or chip off while eating; complicating the treatment plan further.