By "inspecting" does that mean that they checked the sensor for dust/dirt? Every camera collects dust on the sensor over time and it needs to be cleaned. There are ways to make it less of a problem--never change lenses, never take it out of the box, seal it inside a plastic box and never touch it again...
Anyway, dust on the sensor is just a fact of photographic life. You need to learn how to clean your sensor. There are several ways and if you ask 10 photographers the "best" way to clean the sensor you will get 11 opinions--each one supposed to be the "only" way you should do it. Do a search here on the equipment forum and you will get lots of information.
At the very least you will want to get a blower and blow the loose dust off periodically. Here is a pretty good one:
http://tinyurl.com/8fhqb3 They make several sizes but they are pretty good items to have. Blowing the dust off is quick and very easy--you will need to read your manual to find out how to open the mirror so you can access the sensor. It is so easy you could do it just about every time you change lenses. It won't take care of everything but it will get rid of the loose stuff.
One more thing to consider is the speck is something on the lens itself. If you have a different lens see if the blob shows up with that one too. If you get it with every lens then that is a sure sign of sensor gunk.