Here's what you need to know.
The 37-year-old and mother of three mentioned the issue to her doctor two days later, and was referred to a local breast clinic. Last week, she was diagnosed with breast cancer.
The dimpling on her skin was the only symptom Warner experienced, and she only knew that it could be a cause for worry because of a breast cancer awareness photograph she'd seen previously.
After her diagnosis, Warner decided to share a photo of her own breast to Facebook in order to spread awareness.
"I decided to do the post almost straight away," Warner told MailOnline. "I was sat in the car park and thought, 'I'm going to put a picture on Facebook.' It's an intimate area and I was nervous about doing it but thought I'd do it in a delicate way and thought it would be worth it if it helped just one person. If I hadn't seen a post like this previously I wouldn't have known that this dimpling was a sign of cancer."
Warner's post has been shared over 1,300 times, educating women about the symptom and reminding them to conduct regular breast self-exams.
According to the American Cancer Society, the most common symptom of breast cancer is a new lump or mass.
However, other symptoms include swelling, skin irritation, dimpling, scaly skin, breast or nipple pain, nipple retraction, and nipple discharge other than breast milk.
Dimpling due to breast cancer can be caused by an underlying mass like a tumor underneath the skin that is pulling the skin inward.
Dimpling or puckering isn't an automatic cause for panic, as it could also be caused by scarring, cellulite, or a condition called fat necrosis, according to the journal of Diagnostic Radiology.
Regardless, Mayo Clinic recommends getting checked out any time you notice a change to your breasts.