Re: Worried about deep inguinal staph abscess
One thing that one has to remember when diagnosing skin and soft tissue infection is that when you are doing it from palpation and visualization alone, you are using SURROGATE markers of infection rather than infection itself. The gold standard of diagnosis of a skin infection is to take a biopsy of the skin, look under the microscope and actually see the bacteria invading the skin structures. However, you can't do this in everyone so instead, you look at the skin for typical signs of inflammation (i.e. redness, swelling, heat and discharge) to make the diagnosis. Most of the time, when you see these signs of inflammation on the skin, they represent signs of infection, but not always. There are skin conditions like pyoderma gangrenosum which also have extensive inflammation of the skin, but these conditions are NOT infectious.
That said post-operatively, there can be lots of inflammation in the skin in the absence of infection. The hardness you describe is something that is common in surgical wounds and does represent inflammation but not infection. As long as things are not significantly worsening and you are systemically well (i.e. no fevers, serious malaise, rigors etc) things should be fine.
Especially with extensive surgical manipulation of an area, induration can be present for a long time afterwards!