Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency help for breathing difficulty, worsening hoarseness, confusion, fainting, blue or gray lips, severe weakness, or rapidly increasing swelling after a burn.
Contact a healthcare professional promptly if the wound becomes more painful, red, swollen, warm, or foul-smelling; develops pus-like drainage; reopens; or is not healing as expected.
New fever, reduced movement, numbness, or color changes in fingers or toes also need timely assessment.
And for anyone, someone who:
Follow-up allows the care team to reassess burn depth, check healing, change the dressing plan, and monitor movement and scarring.
These symptoms are different from concerns that can wait for routine follow-up.
The article also says
Keep scheduled wound checks even if pain is improving.
Follow the instructions provided for bathing and dressing changes.
Keep dressings clean and dry unless told otherwise.
Do not use adhesive material directly on burned skin.
Once the wound has fully closed, the new skin may remain sensitive, dry, itchy, and more likely to burn in sunlight.
Ask the care team about moisturizers and sun protection.
Every sign above is quoted from the sofidex article on Burns. If you are not sure, err upward — it is always reasonable to be checked.