I'm not a medic, but have some practical experience, and yeah, deep subcutaneous infections are a thing. Tetanus, for example, and some forms of staph. Various anaerobic bacteria, mostly nasty. If that is the case, Sigrun may be feeling general malaise, mental fogging, maybe a slight fever......which could get a lot worse, quickly, once her normal inhuman vitality runs down - say for example if she is wounded again, or gets really hypothermic or exhausted, or majorly stressed out, or catches the 'flu....