。
I have a sharp, stabbing pain right here.
Literal
Here [subject-が] as-if-stabbing hurts.
差し込むように痛む 'hurts as if something is stabbing in' — 差し込む 'to insert, to stab in' + ように 'as if' + 痛む 'to hurt.' This is medical descriptive language — the kind of phrase used when describing symptoms to a doctor. ここが identifies the location of pain.