The regurgitation means the leaky valve.....leaks. They are all meant to be one-way valves. They open outward with the flow, and when the contracting pump/ventricle relaxes and the flow ceases, those leaflets close and prevent backflow...regurgitation. Picture the left ventricle as it pumps blood through the aortic valve, forcing oxygenated blood up and over the aortic arch where gravity would want to take over. That valve opens outward, (up into the aorta) toward the direction of flow. When the flow ceases and the ventricle fills again with the atrium's flow through the one-way mitral valve, the aortic valve closes to prevent the blood column still in the aorta from falling back into the ventricle due to gravity.
What is being regurgitated was your question. Blood. No harm to the blood or to the heart, but it makes the heart very inefficient as a pump. Even mechanical pumps have check valves and other parts to improve the flow, to check the flow, etc. The heart is no different. It has four valves: on the left side, the mitral valve and the aortic valve, and on the right side, the triscupid valve and the pulmonary valve. They all open with the flow/pressure to allow blood to move in one direction, which is what each of the four chambers of the heart are meant to do. Then, they close and prevent backflow so that the filling chamber can more easily force blood into the bigger ventricles, the big pumps.
I hope that all makes sense.
As for cholesterol, it can be controlled by diet to an extent (limited for some people, quite a lot for others), and that depends on the other component, genetics. I can't comment about a statin and finances, but if it comes down to a blocked artery, you would neet a bypass/stent. This would ideally come from frequent monitoring/imaging so that you don't have a high risk of a heart attack before they say to you that it's time to have that heart operation.