When you shake the cartridge, it may form air bubbles inside the cartridge.

Does it harms? It depends. The most critical is not to have air bubbles in the print head. Popular terms is air bubble trap. When you shake the cartridge, the air bubbles will form in the sponge. If this happen, just leave the cartridge overnight, the air bubble will goes up eventually.

If the print head have air bubbles then the quick solution is to perform head cleaning (instructed from your computer). The head cleaning is like flushing the ink into tiny hole inside the print-head. Of course, this will reduce some of ink in your cartridge.

If you can wait, don’t force it. Leave it overnight. Let the air bubble release themselves. If the problem still persists then you need to perform head cleaning.