Removing IKEA "Vikarn" shower-curtain rod
The cap is very similar to a most any plastic lidded container with a tiny lip clicking over another tiny lip. UnhandledExcepSean would be correct that a little pry with a thin stiff device should pop them apart.

Sometimes in just 1 spot is all that's needed and other times you'll need 2 devices and walk the prying halfway around before they pop free. It just depends on precision and quality control differences between the caps, if any.