If WhatsApp opens up to a conversation, tap the back button in the upper-left corner of your screen to go back to CHATS.
Seeing only one tick mark doesn’t always mean you’re blocked. Your messages may not be delivered because of bad cell service. If you’re not sure, you can check the tick mark again at a later time to see if your message was delivered with a delay, or try sending a new message. If you’re blocked, your contact will never receive any of your messages even if they unblock you later.
Any WhatsApp user may choose not to use a profile picture, or remove it if they previously had one. You will always see the figurehead icon if you’re blocked, but it doesn’t always mean you’re blocked if you see the figurehead instead of a photo.
Any WhatsApp user can turn off their last seen and/or online information from their Settings. You will never see your contact’s last seen information if you’re blocked, but it doesn’t always mean you’re blocked if you can’t see it.