Dermatology Questions? Ask an Online Dermatologist.
Was the area whitish before you put Sudocrem?
It seems to be abrasion with the saddle because of cycling. You should use antibiotic cream such as Neosporin and avoid cycling until it heals. Use a better saddle.
If the white is easily removed, it could be fungal infection. But If not, you don't need to be concerned about it.