if you dont know what you're doing and its fine sand...do not touch anything.... send it in to manufacturer or a reputable outside shop (search around, Camera Hospital is one recommended reliable place eg) for a proper cleaning job
sorry without seeing the lens, its impossible to tell how serious yur situation is
You can clean the exterior of your lens and body. If you camera sensor is dirty get a eclipse and swab it. The only no no is to dismantle your lens. You gotta check whether it affect the quality of your picture. If yes get it to lens manufacture, it cost around $60-$120 to get it clean. I do a number of assigment in Egypt and UAE my non weather resistance lens often stuck with some fine sand in the lens which is difficult to clean it.
Btw, you gonna know the difference between sand and dust. Dust may look like small sand particles but fine sand usually cover the entire element, not a few dots here and there those are 80% dust. Logically thinking, if you bring it to the beach and happen the wind is strong and the sand flew up and get into the lens. Hardly is only a few particles.
Yes, this should be my case. The sands get into the lens which makes it not so smooth when tuning the focus. For the camera body, definitely two big spots on all my pictures, i will try with the blower first to clean the sensor and leave the lens to the outside shop.