What can I do about this spot on my lens?

Started 3 months ago | Discussions thread
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Catspaw Regular Member • Posts: 118
What can I do about this spot on my lens?

Its a Sigma 150-500. The spot is only on this lens, without the UV filter. I've cleaned and inspected the objective lens and did the unspeakable: cleaned the back element - with a Nikon alcohol lens swipe - with no success. I increased the contrast on this pic to better define the culprit for display here, but it is quite noticeable in all my pix with this lens and time consuming to edit out.
Input, discuss, suggestions please?

I've heard of internal mold.  Is this what it looks like?

Where can I send it for repair if it comes to that?

Spot from 150-500 Sigma.

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Catspaw.
Fair Winds & Following Seas.

 Catspaw's gear list:Catspaw's gear list
Nikon D7000 Nikon AF-S DX Nikkor 18-135mm f/3.5-5.6G ED-IF Nikon AF-S Nikkor 70-300mm f/4.5-5.6G VR Nikon AF-S Micro-Nikkor 105mm f/2.8G IF-ED VR Sigma 150-500mm F5-6.3 DG OS HSM
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