My best guess is a lymphocele. These can appear where you indicate you are noticing this, can be cord like, are more pronounced during things like masturbation, or after sex. Lymphocele. This is a hard swelling that suddenly appears on the shaft of the penis after sex or masturbation. It happens when the lymph channels in your penis are temporarily blocked. The swelling is made up of Lymph which is a clear fluid that forms part of the body's immune system. But, as stated, I'm guessing from your description. Can you see a doctor? That would be the best thing. Usually will goes away without issue. But again, see your doctor.
The other idea would be that this is a pearly papule. These could be like a grain of rice. But they are normally more toward the head of your penis. That's not something that is absolute though. https://www.healthline.com/health/mens-health/lump-on-penis#lymphoceles
Let me know what you think.