Brief Answer:
please give additional information.

Detailed Answer:
Hi.
Thanks for your query, albeit short and specific.

Read and understood that 2 pillar (sebaceous) cysts were injected with steroid.
Now have a lump at left temple not as hard, but like a quarter size.

Please give me additional history for me to assist you more:
- When where the cysts injected?
- Is he lump elevated patch of skin?
- Is there any redness or itching?
- Has it developed within half hour of injection or later?
- Have you taken any medicines?

Please post the clear pictures if possible so that they will help me for on-the-spot diagnosis.

The possible reason can be an allergic urticarial rash.

I hope this answer help.
Please give me the feedback.
And take antihistaminic tablet if you have at home- like Cetirizine or Benedryl.

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Brief Answer:
can be Dermatitis

Detailed Answer:
Thanks for your feedback.
Noted that cysts were injected in Aug 2015 and hence may not be related to the present problem unless the cysts were present at the same spot.

Also noted that you have a tooth extracted last Monday on the upper left side; the patch of skin is elevated without rash, redness or itching which developed 3 days ago.

The commonest cause can be:
Urticaria, meaning an allergic reaction of the skin like angioneurotic edema wherein there is no redness, or itching.
Could have been due to insect bite.
Dermatitis in a patch appearance.

Please take antihistamine and if it does not respond to it, consult your GP/PCP or a Dermatologist.

Your posting a clear picture would have helped me to do on-the-spot diagnosis.
Please try to post a picture/photograph for me to understand better and assist you further.

I hope this answer helps you.

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