If she is not licking it or trying to scratch it, just leave it alone and keep an eye on it. It could change, get bigger, or just go away. If it does not appear to irritate her, I would just let it be and watch it.
It could be something, or nothing. One of my dogs once had a crusty bump on her back about the size of the little finger nail. I forget what my vet called it, but he said it was nothing unusual, but she was 9 years old.
You may be able to find a photo of it online by searching a description of it. If it concerns you after a few days, I would let your vet see it, but if medication was called for, I would want a good explanation at to why. 1 year old is pretty young to require meds, IMO.
Also, feed her good food. Don't fall for advertising HYPE by the dog food manufacturers. For example, IMO 'Beneful' is low quality, and Hills Science Diet is not much better. Research quality dog foods. It will depend how much you want to spend, but ALWAYS 'read the ingredients'. A 'sole' meat should be the FIRST ingredient......not yellow corn. It may be beef, chicken, turkey etc.. And avoid them if they list 'meal' or 'by products' in the ingredients.
I would also get some 'pro-biotics' into her.
OH MY,how come our minds go to the "panic,I know it is the
BIG-C...and we fret outselves into major worry and upset,so
DEEP BREATH...it is not an emergency...as Kerek@ said,do
watch her...do you have any Neosporin with pain relief" put a
dab on it every 3 hours or so,softens the lump and if it has an
open part,will soothe and disinfect...just a thought?
First it may well be a simple scratch that looks awful-it may
be a wart,oil gland plugged,cyct(non-malignant) or a hair
folicle that is plugged,got infected...now see,lot-sa things to
think about...you could use a TEPID wash rag,being VERY
gentle,DAB IT,wipe it,no rubbing just to clean the area a bit
let it dry before using Neosporin..NO peroxide (ouch) NO
IF it is not better by Monday by all means let the vet have a
look( to ease your mind)they may draw a bit with a needle
byopsy to look at cells,( IF they think it's needed) then do
little check under the microscope?
FYI I have a 'lil blue colored Chi who is 4, now he tends to get
some little "warts" off and on but they go away on their own,
I was told it was a possible effect from his being the color he
is(?) but I think he just got a bit of a "wart virus" they last for
a month to 6 weeks...not an issue,no biggie.
I AM SURE Trixie will not have a major problem,it JUST came
up, is not a long term issue but Kerk2 made some excellent
points...WHAT kind of food is she eating,yes, this could be a
problem, also,my Nana used to say,"you are what you eat" so
a good thing to ponder and consider?
BY ALL MEANS,relax,you can't do anything until the vet opens
so relax,"let it go" and if still worried,by all means take Trixie in
for an exam...it will be ok, she is just out of her "puppy" stage.
BTW...Havanese are pretty strong,hearty dogs as a breed...also