bad at socializing; poor social skills
Describes a person who is awkward or uncomfortable in social situations, often used self-deprecatingly.
I'm bad at socializing and not good at going to parties.
He has few friends because he's a poor mixer.
人見知り refers specifically to shyness around strangers, while 交際下手 is a broader term for being bad at social interactions in general.
社交的 means 'sociable' or 'outgoing', the opposite of 交際下手.
Compound of 交際 (kousai, 'socializing') and 下手 (heta, 'unskillful').