Muck around with
Definition 1 of 2
Pro Tip 1/3Skill Level
Used when someone lacks expertise but still tries to do something complex. 
He tried to muck around with the computer code and ended up crashing the system.
Pro Tip 2/3Potential Harm
Implies that the person’s actions might cause damage or problems. 
You might erase important files if you muck around with the software settings.
Pro Tip 3/3Casual Warning
It's a light-hearted warning to not interfere with something. 
Please don't muck around with the thermostat; it's very sensitive.