Anxiety about the penis size does not mean that a person has smaller manhood.

Around 46 of the recruited men also agreed to have their penis size measured up, both when flaccid and erect.
The researchers found that around 30 percent of the men were unhappy with their penis size while 35 were content, with the remaining falling between being happy and unhappy. Older men and homosexual men were the most anxious about their penis size. The size of the penis of those measured ranged from seven to 10cms long and seven to 13cms in terms of girth when flaccid but stretched and 10 to 20cms long and nine to 17cms in girth when erect.
Source-Medindia