pimple
皰 centers on a small skin blemish: a pimple. It is a specific term for that raised spot on the skin.
皰 combines 皮 (skin) with 包, which likely contributes the sound and the idea of something contained or raised, together suggesting a raised spot on the skin.
Skin 皮 with a wrapped 包 bump: a pimple is a small raised spot wrapped under the skin.
For ホウ, imagine a pimple so big it makes a hollow in your skin when it's gone: hollow -> ホウ, and the pimple leaves a hollow.
pimple; acne