Inwards means toward the inside of something. You fold a letter inwards. A door may swing inwards. A pain may spread inwards from the skin. In British English this -s form is common; American English more often uses inward for the same direction. Though actually, inward is also an adjective (“an inward calm”), while inwards is almost only the direction word. There is an old noun inwards for an animal’s inner organs, but students can leave that on the shelf — it is rare now. The word you need is the adverb: movement from the outside toward the centre.

向內；朝裡面