If you have only used your fingers and haven't tried a wrench on it, I wouldn't think it unreasonable to try to tighten it with a wrench using sensible torque (below bolt spec.). Get a new drain plug, also; it's great for peace of mind to have a spare in the trunk.(and cheap).
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)