Spills happen, even when you're careful. Whether you create the spill or just come across it, always report a spill. If you can report it immediately by radio or cell phone, then do so. Otherwise, report it from a safe place as soon as is practical.
Don't assume you must clean it up or even contain it; you might not be able to do either. If the spill is more than about a gallon, don’t attempt to clean it up. If you can toss down some absorbers to slow the spread, fine. Then leave. If your eyes burn or the fumes make you cough, don't do anything except get out of there.
As you leave the area, alert others in the vicinity. Contact your boss and report the spill. Briefly state how you handled the incident and why. A properly equipped spill team must respond to handle some spills; make sure you and your boss have reported the incident to the correct contact so this team will be assembled and dispatched.