There are no exercises or creams that increase penis size. Puberty happens at different ages and speeds, though most males will be fully developed by the age of 20. During puberty, it is normal for boys to be concerned with how their bodies are developing, and to compare their penis size with other males. 

If you worry a lot about the size of your penis, or you are late in going through puberty, speak with a health care provider who can give you some guidance. A good question to ask your health care provider is “What is the normal penis size for someone my age?”

for more information about penis size: http://www.scarleteen.com/article/advice/shown_actual_size_a_penis_shape_size_lowdown