Anal itching (also known as pruritus ani) can occur for other reasons. Not cleaning completely around the anus after defecation, heavy garment wearing during the humid, hot temperature, a rash, and in some cases, anal fissures (break or deep cut in or around the anus). If you had herpes, the itching would have come along with herpetic blisters already formed.
Thank you for your comment. The anal itching has been quite severe yesterday and today. I'm aware this is one of the symptoms for genital herpes. Is this just a coincidence this is happening?
You really do not have much to worry about from this exposure. The blood on the tissue could be the fact you rubbed too hard after defecation and the pimple you may have found may be normal acne or just hair bumps, really. Frottage doesn't pose much risk in terms of std transmission and most commercial sex workers are often checked for stds, not for business' sake but, for self's sake. If you want, you can get tested for peace of mind. Otherwise, there is not much to warrant any concern for std transmission.