No oil pressure-stop asap! Engine started knocking car has 115k

Hello, Besides the fact that someone sold you a car with an obvious problem, you likely have an oil pan that needs to be resealed. On this engine, the oil pump delivers oil to the engine through passageways in the oil pan. The seals between the oil pan and the engine block can leak and cause the exact issue you are experiencing. It's very common on these Volvo engines. The fix is to remove the oil pan and replace ALL the oil pan and oil pump pick-up seals. Good Luck