What an unfortunate accident! It sounds quite painful and frustrating, and hopefully you will be back to your normal self in no time. You are absolutely correct that with any kind of injury
with skin breakdown like this, it is very important to make sure that infection does not develop. This could be quite problematic if an infection were to involve the joint space itself, so it is important to discuss any concerns with your physician. If you are concerned that the wound is leaking material that concerns you, you should definitely make sure your physician assesses the area to make sure that you do not have a developing infection.
From what you describe, it sounds as though the moisture from either a shower or the antibiotic ointment is causing some changes in the appearance of the scab. A scab in any location will look "yellowish white" if allowed to soak in water. In addition, healing incisions will often drain small (sometimes not so small) amounts of what is called serosanguinous fluid. This is not a concern but rather just part of the healing process.
However, it is always better to be safe than sorry in this kind of a situation, and the most important way to make sure you do not have a developing infection is to have your physician take a look at the laceration.