Sore thickened area evening after Botox injection, but no bruising--normal?

If I had to guess I would say you have a deep bruise under the skin. A photo would help to give you a better answer.

It might be that there is an underlying bruise which has not surfaced or individuals who have sensitive skin might have some irritation. I would follow up with you injector. 

Hello and thank you for your question. Based on the symptoms you are describing it sounds like you developed a small bruise underneath the skin. These don't always turn purple/dark as most bruises do. The area should improve with in the next 5-10 days. If things don't get better day by day I would suggest you go back to the office where you were treated for an assessment. Hope this helps, Dr. S. 

I suspect you have a small bruise under the skin that hasn't yet come to surface. This is causing your soreness which should resolve on its own over the next few days. 

This is an excellent, and common question.
Immediately after Botox injections you may notice a raised bump with some mild tenderness.  These will usually resolve fairly quickly - within hours.

It is probably a vessel that has leaked some fluid but you don't see the bruise yet at just a few hours.  this will go away on its own in a day or so and not to be concerned

I'm sorry to hear about your discomfort. Most likely there is a small bruise but it's still deep and has not had a chance to come to the surface. Apply a warm, moist compress and this will help you. Good luck from New York City

The botox itself is not painful, but the secondary swelling from your body and the fluid pressure can make it sore until the fluid reabsorbs.
In my experience, time and patients, light massage, and cool compresses will help.
Dr Kristine Brecht
Seattle, Wa