It sounds like your frame has been compromised. It may hold up for awhile -- maybe even a long while -- but the stresses of normal riding -- not to mention the stresses of hitting another big pothole! -- could cause the tube to fail. If you are lucky, the frame with fail gradually rather than catastrophically.

If you choose to continue to ride the bike, monitor the damaged area frequently. If you notice even the smallest sign that the ding has worsened, get off the bike, and don't get back on.

One of my steel bikes developed two small dings in the head tube and one in the top tube, and I continued to ride for three seasons without the damage worsening. But then sanity prevailed, and I replaced the frame.