Locate your oil filter. It should be in the same area, just above the filter. It is important if you want to know how much oil you have in the crankcase, and how much pressure your oil pump is pushing the oil throughout the engine to lubricate and cool off to prevent the engine from overheating.
Over time, leaks do happen. You may able to get off by taking the sending unit out (while doing oil change, so you won't lose any oil), clean it, put new teflon tape, and re-insert the unit, and tighten it. If that doesn't work, get a new unit, should be around $30.
If you were to have someone fix it, it will be one hour labor.