Patience grasshopper! If it was aptasia, I don't think it was, It would not have become a problem for a while. In the mean time you could let it get bigger and really see what it was. I think it was some kind of soft coral or polop. I think you just killed your first coral, at least you got that out of the way!! every thing else(with the exception of bubble alage) is normal and healthy. Be patient, I know, it's hard, but it will be worth it in the end.