Is 10 mg of iron in a multi vitamin too much if I do not need extra iron? I took a multi with this amount for the last three days.

Not a problem. If you get enough iron in your diet (e.g., meats, beans, fortified cereals), and are not low on it somehow (e.g., women losing it with heavy periods) you won't need to take extra iron. However, the amount you mentioned is not a lot of iron. For comparison, a packet of oatmeal has approximately 11 mg of iron.
Not a problem. Your body has a unique ability to bind with and take in iron as it needs it or let it pass into the poo when it doesn't. At 10 mg you will never need to worry about any overload--ever.