My girl was 12 before I had her noticeable hernia repaired, at the same time as her de-sexing. Don't rush it, as long as the vet does not think the gut is caught in the gap in the wall of the stomach, she will be fine. Remember, these dogs are usually low vet patients, but I have had them checked over about every 12 months.
Regarding the pimple, it might be just the scar left over the stitches, when my surgery was done I had a similar reaction, that did not require any intervention except time. However, get a knowledgeable person/vet check the abnormality, to be sure. The American vets are taught that de-sexing must be done as it causes cancer! What a load of horse apples! De-sexing, castration in males, and a hysterectomy in females, is not normally necessary. Perhaps females may be done later after child-bearing age, and males are done later in life as well . Watch out for legislation, as no one is our State of South Australia is allowed to have an entire breeder, unless they are registered. That takes care of random mating.