Custom Size Hickory Butcher Block - Prefinished

I applied the oil as recommended for the first 7 days. After 4 weeks, the surface seemed to become a little rough. Is the natural and if so, can I use a finishing sandpaper to smooth it down a little. I am getting ready to apply to monthly application of oil. Otherwise, the top is everything thing we were looking for. It compliments our kithcen very well.