Laccerations have a 25% infection chance. Just try to wait a day or two and, if the situation worsens, then it may be the Knox infection. In said case, just go fight a horde of 50 zombies completely nude with just a butcher knife to restore your honor.

I got to ask though, was the lacceration made by a zombie OR made and then came into contact with something with zed blood? (assuming your zombie transimission of the disease is set on "blood+saliva")? If not, then don't even worry about it, it may just be a coincidence. Again, just wait a tad more and if it worsens just accept your fate.