You have a bad bearing. If you keep driving it without repairing it you are likely to get a connecting rod through the side of the block. You first need to pull the oil pan off and see if it a rod or main bearing. It sounds like a rod bearing a you could get by just putting in a new rod and crankshaft, that is the budget deal but I would recommend at the least put in a rebuilt short block and the best option is a rebuilt long block. If you are skilled you can rebuild it yourself.