Brief Answer:
Yes, friction is the most likely cause

Detailed Answer:
Hello sir and welcome.

Thank you for writing in.

From the description provided, it does seem like this wound/injury is purely due to friction from dry or non-lubricated intercourse.

If you do not mind, could you answer a few questions of mine sir? Have you experienced any swelling, boils, lumps, blisters, etc; around your penis previously? Is your sexual partner a know person or not? Are you experiencing any symptoms other than swelling?

To avoid such a problem, you could use the following suggestions:
-Indulge in more foreplay, this will help in giving ample amount of time to your partner to lubricate, which will avoid friction
-Use a lubricant. Many lubricants are available over-the-counter that are safe to be used during intercourse. Vaseline is also considered safe and is popularily used
-Use of condoms. Condoms come well lubricated and prevent friction and spread of infection, along with the prevention of unwanted conception

I hope you found my response helpful sir. Looking forward to hearing from you. In the meantime, keep your genitals clean and dry. Avoid all forms of sexual contact and masturbation. Wear loose and comfortable, preferably cotton undergarments till your wound helps.

Best wishes.

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