Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services or go to an emergency department for bleeding that does not stop with firm pressure, a deeply embedded object, exposed bone, loss of part of a finger or limb, severe crush injury, or signs of severe blood loss such as fainting, confusion, or marked weakness.
And for anyone, someone who:
Seek prompt medical advice for increasing pain, warmth, redness, swelling, pus, bad odour, fever, red streaks, or a wound that starts opening.
New numbness, weakness, reduced movement, pale or blue skin, or persistent bleeding also needs urgent assessment.
And for anyone, someone who:
Contact your healthcare team during routine hours if the dressing repeatedly comes loose, drainage continues, the wound is not improving, or you are unsure how to change the dressing.
Also call if you need clarification about bathing, work, activity, or stitch removal.
Every sign above is quoted from the sofidex article on Cleaning and bandaging a wound. If you are not sure, err upward — it is always reasonable to be checked.