Enlarged Paraaortic Lymph Node Noted at CT Scan (2.5cm *2.5 Cm). Should I Worry?

It is impossible to tell exactly what is doing based on that photo. I would consider Tinea Versicolor, which is caused by a yeast, to be a possible cause.

The bug bite was most likely a co-incidence. Chronic inflammation seems to be a factor in the development of squamous cell carcinomas, especially of the oral cavity but basal cell carcinomas have not been linked to bug bites. 

You should be washing the area with light suds during your shower. You can get this from antibacterial soap, but even suds from shampoo should help. Often, I'll have patients use a small amount of hydrogen peroxide on the healing surgical wound itself to help remove crust. But being four days...