English Sentence
Tom twisted his ankle and it swelled up.
Tom se hinchó, ¿como un sapo?
Tom se torció el tobillo, que se hinchó. [?]
Tom twisted his ankle and it swelled up.
Tom se hinchó, ¿como un sapo?
Tom se torció el tobillo, que se hinchó. [?]
Spanish allows for null subjects, and Spanish language tends not to be overly specific when the meaning of a sentence is obvious, so having the ankle as the implied subject for the second verb seems fine to me.
“se le hinchó” but "se hinchó " alone sounds correct too, since it’s obvious that it’s about the ankle