My wisdom (or molar) has a large cavity hole in it. What should I do?

i am unsure if it is a wisdom or a simple molar, but the far most back tooth on the upper left of my mouth has had a cavity in it for awhile. up until recently the cavity has turned into a rather sizable hole, allmost taking over half the tooth. there is no pain, but the tooth hole itself is becoming jagged & a tad bit pointy, not so much that it could cut flesh, but it may come to that point soon. will it fall out naturally, or do i have to have it removed. & if so, how much will it cost?