Brief Answer:
Cellulitis, striae, infections of skin, etc.

Detailed Answer:
Hello sir and welcome.

The causes for a presentation similar to yours are a few, let me list them for you along with a few of their symptoms so you could relate to them:
-Cellulitis: Red streaks, swelling, warmth of skin locally, redness, pain or tenderness, etc.
-Lymphangitis: Is unlikely due to the location; but fever is quite commonly seen, along with site of infection being quite obvious
-Infections of the skin: Resulting from break in the skin or other conditions like psoriasis, etc; present in the form of red streaks under skin
-Injury: The skin in the described region is quite thin and once healing begins (after an injury), the scar tissue formed can initially look like a red streak. Do you recall any injuries to the region?

If you can describe the lesion and also upload a photo of the lesion, I will be better able to help you.

I hope this helps. Do write back to me for any further clarifications.

Best wishes.

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Brief Answer:
Superficial injury streak

Detailed Answer:
Hello XXXXXXX

Thank you for the image and for writing back.

From the image the streak looks more like an injury, something very superficial, yet something that should disappear soon. Could you tell me when you first noticed this sir?

It does not look like anything serious and as you rightly said, it does not match any of the above mentioned conditions either. I am sure you have just bruised yourself unknowingly, and this shall soon subside. From the length and edges, I can clearly say that there is no specific anatomical structure beneath the streak that could have caused the region to develop a red streak; thus ruling out all serious conditions. That means, this is mostly due to some kind of an injury. Apply warm compresses to the region which will increase circulation and promote healing.

Hope this helps sir. Please write back to me for any further clarifications.

Best wishes.

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