NOT SEXUALLY ACTIVE
Itís not possible for it to be an STD if you have not had sexual contact with another person. Many guys like to use water-based or silicone-based lubrication when masturbating to prevent chafing. A little lube or lotion afterwards can help, too. If you're already using some lube, it's possible the irritation might be an allergic reaction. Try switching brands and see if it helps.
To find out if your penis irritation is from too much "rough" masturbation, you might want to experiment a little. Try masturbating in other ways besides just stroking the glans. Many men are stimulated by erotic images, or from stimulation of other parts of their body -- anus, nipples, etc. The "The Complete Guide to Safer Sex" by the Institute for the Advance Study of Human Sexuality may help you find additional creative ideas. You can find it online at Amazon or at your local bookstore.
To your health,
STD TRANSMISSION AND PREVENTION ADVICE
Latex, polyurethane, male, female -- we've got the lowdown on them all.