That will indeed help him get back to safety without bleeding out! While lodged in his abdomen it seems to remain mostly tangible, unlike the rest of the body, before melting out as a thick black goo within a few hours.

For a week after escaping the mines, Javert will cycle through bouts of nausea and fever, and a deep longing to find and serve the seven-eyed creature once he's well enough to walk. Of course, likely by the time he's actually well enough to walk he won't want to anymore - but he'll sure remember how important it felt to find the green-eyed spirit and do its violent bidding.