有点儿 (yǒudiǎnr) is an adverb meaning 'a little, somewhat', used before adjectives to soften a negative or undesirable quality (e.g., 有点儿冷 'a bit cold'). It differs from 有些 (yǒuxiē), which can also mean 'some' (a quantity) and is used before nouns; 有点儿 only modifies adjectives or verbs. 一下 (yíxià) is a verb complement for brief actions, not for degree.