Black spots showing up on my MacBook screen

Before anything else, wipe it. Spots that turned up after the lid was closed are often just marks off the keyboard keys - a slightly damp microfibre and they're gone. If they stay put and show over every colour, take a screenshot: if the spots aren't in the screenshot it's the panel itself, dead pixels or pressure damage from closing it on something. That's a display replacement, so check applecare before paying for it.