Pilonidal cyst recurrence or residual disease: Given the history of pit excision for pilonidal disease, it's plausible that the patient is experiencing a recurrence or residual disease, especially if the area of tenderness is near the previous excision site. The absence of new pits, induration, abscess, or discharge does not rule out this possibility, as early or mild recurrences might not present with these classic signs.

Folliculitis or furuncle: These are common conditions that could cause localized pain, swelling, and tenderness in the gluteal area, especially if the patient has been shaving or has had skin irritation in the area.
Epidermal inclusion cyst: This could present as a small, tender swelling, especially if it becomes inflamed or infected.
Hygiene-related skin irritation: Given the location at the gluteal cleft, skin irritation from friction, sweat, or hygiene products could cause discomfort and swelling.

Abscess or infected hematoma: Although the area does not currently show signs of an abscess (such as fluctuance, significant induration, or discharge), an early or deep abscess could present with pain and swelling. Similarly, an infected hematoma from the previous surgery could cause these symptoms.
Necrotizing fasciitis: This is a rare but serious condition that could present with pain, swelling, and tenderness, especially if there's a history of recent surgery or trauma. Early recognition is crucial.
Osteomyelitis or sacrococcygeal infection: Infection of the bone or the sacrococcygeal area could cause deep pain and might not always have obvious signs of infection like fever or discharge.

Hidradenitis suppurativa: Although more common in the axillary or groin areas, hidradenitis suppurativa could potentially occur in the gluteal cleft, causing recurrent, painful nodules or abscesses.
Gluteal cleft lipoma or other benign tumors: These could cause a painless or occasionally painful swelling but would be less likely to cause acute tenderness without a history of trauma.
Inflammatory bowel disease (IBD) related complications: Very rarely, conditions like Crohn's disease could cause perianal or gluteal disease, including fistulas or abscesses, though this would typically be accompanied by gastrointestinal symptoms.