gnaw, bite, nibble
齕 centers on using the teeth to cut or wear away something small: gnawing, biting, or nibbling.
齕 combines 齒 (tooth) with 乞, which likely contributes the sound. The character expresses actions done with the teeth, such as gnawing or biting.
The left side 齒 shows teeth, and the right side 乞 looks like a person bending down to nibble. Picture someone gnawing on a bone with their teeth.
For コツ, imagine the sound of a hard bone being gnawed: kotsu kotsu. The kotsu sound cues コツ while the teeth work on the bone.